It is known to provide wheelchairs with mechanisms for locking the wheels thereof, preventing the wheelchairs from traveling except at the urging of the user. Standard wheelchair locks must be operated from both sides of the chair, that is, the left wheel must be locked from the left side, and the right wheel must be locked from the right side. However, often individuals requiring wheelchairs suffer from greater weakness in one side of the body than the other, such as for example stroke victims. Such persons must either reach across their body with the stronger arm and hand to operate the opposite wheel lock, or require assistance from another person.
There have been attempts to address this deficiency of conventional wheel locks. For example, U.S. Pat. No. 4,809,818 to Leggett et al. provides a dual braking structure consisting of a rod 14 attached to a first wheel lock or brake, a center section 46, and a left rod 24 attached to a second wheel lock. Thus, both brakes may be operated by actuating either brake. Center section 46 allows left and right rods 14, 24 to be folded relative to one another when the wheelchair is folded.
U.S. Pat. No. 6,443,268 to Dearth et al. provides a similar assembly for linking operation of two wheelchair locks or brakes. A crossmember 38 comprising paired segments 42 pivotally coupled at their interior ends is connected to paired wheelchair brakes at the exterior ends of paired segments 42. Accordingly, operation of both wheelchair brakes may be accomplished by actuating either brake. Because of the central pivoting coupling, crossmember 38 may be folded when the wheelchair is folded.
These devices appear generally effective for their intended purpose. However, significant improvements are possible. Use of a bar or rod to link paired wheelchair brakes or wheel locks adds weight to the chair, particularly when a sufficiently thick material is used to prevent the twisting or torsion inherent in applying a force to a single end of a bar or rod. Particularly in the case of a weakened user of the chair, any savings in weight is advantageous in terms of user comfort and convenience. This extends to the comfort and convenience of persons assisting the wheelchair user.
The stopping power of a conventional wheel lock or wheel strike is provided by frictional force. Therefore, to be effective a wheel lock must contact a wheelchair wheel with the required amount of force to substantially prevent rotation thereof. This force is provided in response to an actuating force provided by the user. In order to increase stopping power, a conventional wheel lock must be caused to engage the wheelchair wheel with increased force. Because the wheelchair user is often relatively weakened, application of additional force may be difficult. Further, materials from which wheelchair parts such as wheelchair locks are constructed have a finite strength and resistance to shear forces, and in extreme conditions may break in response to the applied force. It is therefore desirable to find means for improving the stopping capability of a wheel lock without necessitating application of increased force.
Therefore, a need in the art exists for a wheel locking mechanism which is easy to operate for persons with partial or total immobility or weakness in one side of their body. Such a wheel locking mechanism should preferably be adaptable for affixation or retrofitting to any standard wheelchair design.